OVERALL OBJECTIVES OF PROJECT: 1. To characterize the membrane receptor sites for transferrin and to determine their role and regulation of intestinal absorption of iron in its subsequent delivery to erythroid cells. 2. To determine the role of iron and pathogenesis of fibrosis and hemochromatosis. 3. To study metabolic abnormalities of iron deficient red cells with specific response to the maintainance of the integrity and plasticity of red cell membrane. GOALS FOR THE CURRENT YEAR: 1. Studies on the interaction of transferrin and cell membranes. a. to identify the reticulocyte membrane receptor for transferrin of the Belgrade rat and to compare it to that of a normal rat; b. to compare the endocytosis of ferritin-antitransferrin by Belgrade rat reticulocytes and normal rat reticulocytes; c. to determine the role of transferrin in the release of iron from the intestinal epithelial cells to the plasma. 2. To study the effect of long-term parenteral iron loading in rats on proline hydroxylase activity, tissue necrosis and collagen accumulation in the heart and liver.